The transcription factors of the nuclear factor κB (NF-κB) family play a pivotal role in the cellular response to DNA damage. Genotoxic stress-induced activation of NF-κB differs from the classical canonical pathway by shuttling of the NF-κB Essential Modifier (IKKγ/NEMO) subunit through the nucleus. Here, we show that DNA-dependent protein kinase (DNA-PK), an enzyme involved in DNA double-strand break (DSB) repair, triggers the phosphorylation of NEMO by genotoxic stress, thereby enabling shuttling of NEMO through the nucleus with subsequent NF-κB activation. We identified serine 43 of NEMO as a DNA-PK phosphorylation site and point mutation of this serine to alanine led to a complete block of NF-κB activation by ionizing radiation (IR). Blockade of DNA-PK by a specific shRNA or by DNA-PKcs-deficient cells abrogated NEMO entry into the nucleus, as well. Accordingly, SUMOylation of NEMO, a prerequisite of nuclear NEMO, was abolished. Based on these observations, we propose a model in which NEMO phosphorylation by DNA-PK provides the first step in the nucleocytoplasmic trafficking of NEMO.

核因子 κB (NF-κB) 家族的转录因子在细胞对 DNA 损伤的反应中发挥着关键作用。基因毒性应激诱导的 NF-κB 激活不同于经典的经典途径，即 NF-κB 必需修饰物 (IKKγ/NEMO) 亚基通过细胞核穿梭。在这里，我们发现DNA依赖性蛋白激酶（DNA-PK）是一种参与DNA双链断裂（DSB）修复的酶，通过基因毒性应激触发NEMO磷酸化，从而使NEMO能够通过细胞核穿梭，并随后产生NF -κB激活。我们将 NEMO 的丝氨酸 43 确定为 DNA-PK 磷酸化位点，该丝氨酸点突变为丙氨酸，导致电离辐射 (IR) 完全阻断 NF-κB 激活。通过特定 shRNA 或 DNA-PKcs 缺陷细胞阻断 DNA-PK 也能阻止 NEMO 进入细胞核。因此，NEMO 的 SUMO 化（核 NEMO 的先决条件）被废除。基于这些观察，我们提出了一个模型，其中 DNA-PK 的 NEMO 磷酸化提供了 NEMO 核细胞质运输的第一步。